A check pending redelivery is read before the let-through fetches (none is handed back);
a deleted module is done for the plan's key; the queue an ask came from is let go of when
it ends. Tries say they run under their own id.
A message that reaches a builder's subscription outside a fetch was held unheartbeated for
the whole run of another ask, behind which a delivery waited (issue 1747). The queues the
running ask did not come from are let go of and bound again after it.
jschoubben